Arsenic is in the environment as a naturally occurring substance or as a contaminant and is found in water, air, soil, and food. Published scientific reports have indicated that organic arsenic, a less toxic form of arsenic and the form present in 3-Nitro® (roxarsone), an approved animal drug, could transform into inorganic arsenic. In response, scientists from the FDA’s Center for Veterinary Medicine and the Center for Food Safety and Applied Nutrition developed an analytical method capable of detecting very low levels of inorganic arsenic in edible tissue.
Using the new method, FDA scientists found that the levels of inorganic arsenic in the livers of chickens treated with 3-Nitro® were increased relative to levels in the livers of the untreated control chickens.
Alpharma, a subsidiary of Pfizer, Inc., decided to voluntarily suspend sale of 3-Nitro® and to facilitate an orderly process for suspending use of the product in the United States. Ownership of the veterinary drug subsequently changed to Zoetis, Inc., who continued the suspension from sale of 3- Nitro®. On February 27, 2014, Zoetis, Inc. voluntarily withdrew the new animal drug application for 3- Nitro®. On the same day, Zoetis, Inc. and Huvepharma AD voluntarily withdrew all new animal drug approvals and supplements for 3- Nitro®, as well as arsanilic acid and carbarsone (two other arsenical new animal drugs) for use in animal feed (including all combinations with other approved new animal drugs).
On April 1, 2015, Zoetis announced that it would discontinue marketing Histostat (nitarsone), the only remaining arsenic-based animal drug on the market, by Fall 2015, and would request withdrawal of the approval for the drug by the end of 2015. Histostat (nitarsone) is approved for the prevention of histomoniasis (blackhead disease) in turkeys and chickens, and is the only approved animal drug for this indication. Histomoniasis is a disease that occurs regionally and seasonally in turkeys, and causes significant mortality. Histostat (nitarsone) will cease to be available in the 2016 growing season.
- FDA Announces Pending Withdrawal of Approval of Nitarsone
- Zoetis Letter of Commitment Regarding Histostat (PDF - 207KB)
- FDA: Pfizer will voluntarily suspend sale of animal drug 3-Nitro
- Questions and Answers on Arsenic-based Animal Drugs
- Audio of FDA Media Briefing on FDA's Study Findings Leading to the Suspension of 3-Nitro (Roxarsone) Sales
- Transcript of FDA Media Briefing on FDA's Study Findings Leading to the Suspension of 3-Nitro (Roxarsone) Sales
For copies of the reports contact: AskCVM@fda.hhs.gov
- Executive Summary - Study 275.31 (PDF - 41KB)
- Executive Summary - Study 275.35 (PDF - 42KB)
- Executive Summary - Study 318.41 (PDF - 66KB)
- Executive Summary - Study 415.06 (PDF - 17KB)
- Arsenic Speciation in Broiler Chickens - Summary Final Report (PDF - 342KB)
- Arsenic Speciation in Broiler Chickens - Amendments to Final Report (PDF - 77KB)
- Arsenic Speciation in Broiler Tissues - Analyst's Report (PDF - 3.2MB)
- Arsenic Speciation in Broiler Tissues - Statistician's Report (PDF - 422KB)
Federal Register Notices
- Final Rule; Technical Amendment; Zoetis Inc.; Withdrawal of Approval of New Animal Drug Applications for Combination Drug Medicated Feeds Containing an Arsenical Drug
February 27, 2014; 79 FR 10976
- Final Rule; Withdrawal of Approval of New Animal Drug Applications; Carbarsone; Roxarsone
November 22, 2013; 78 FR 69992